Hi Wim - are there overlaps or collisions in group or object or layer names in the two files? OBJ import has so many settings for how to treat objects and groups and layers, it seems a clue would be in that part of the process. Can you send us those? Oh, I see the link… thanks.

@wim - both files’ mtl files have the same exact names inside - only the bitmap changes, so I guess Rhino currently thinks they are the same material… so far just mucking around here, I can’t find a way to name these that avoids the overlap though… still poking, I’ll probably need to check with Tim on this one.

So, yes, the material names are the same but I would think that Rhino should be able to update map_Kd Bus_0.jpg with map_Kd Compressor_0.jpg. Perhaps with a Warning - Existing Material Found: Replace / Rename / Cancel question?